Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

504
FXUS63 KLOT 051852
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
152 PM CDT Sun Jul 5 2026

.KEY MESSAGES...

- Isolated to widely scattered showers and thunderstorms are
  possible (20-40% chance) this afternoon mainly near/south of
  I-80, but most areas will remain dry.

- Drier and more seasonable conditions are expected to start
  the week before stormier weather returns late week.

&&

.DISCUSSION...
Issued at 152 PM CDT Sun Jul 5 2026

Early this afternoon, we`re finding a cluster of light to
moderate showers stirring over the lake. This cluster was
brought on by a vort lobe spinning over the southern end of the
lake about the back end of the departing trough. Notably weak
convective layer shear isn`t helping move these showers along
very well as they track toward the south at near or less than 10
mph. Latest radar trends suggest that this activity should
target portions of northwest Indiana within the next couple of
hours. However, the southern extent of the showers has been
fizzling away as of late and they may even fail to survive to
the shore.

Coverage of isolated to widely scattered showers is anticipated
to blossom and spread inland away from the lake as we progress
through the afternoon, especially near and south of I-80. The
greatest forcing tied to this vort will focus over the southern
half of the CWA and a northeasterly low level wind field will
continue to spread cooler, more stable low level air inland from
the lake. Meanwhile, instability continues to build across
outlying areas with several hundred to around 1,000 Joules of
largely uncapped MLCAPE south of I- 80 and especially south of
the Kankakee River expected for the mid-late afternoon. Latest
CAM guidance generally favors areas near/south of the Kankakee
River during the latter half of the afternoon and into early
evening for the highest (still widely scattered) precip
coverage. A handful of thunderstorms will be possible down in
these parts as well. The limited instability and weak shear will
inhibit a severe threat. However, the plentiful moisture, poor
shear, and limited forcing beyond the low levels could make for
slow-moving low-echo centroid pockets of heavy rainfall. Should
a heavier shower or storm linger over an area that saw lots of
rain or any flooding over the past few days, minor flooding
impacts could be reinvigorated, although this is a low and
isolated potential.

Farther north up into the Chicago metro and west of the
lakeshore, the environment appears most supportive of precip as
of this writing during the early part of the afternoon than
later in the day. The footprint of the vort looks to spread
inland carrying the better large scale forcing farther south for
the mid-late afternoon. An isolated thunderstorm can`t be ruled
out north of I-80, but the odds are best prior to 3-4 PM.
Additionally, a secondary vort ejecting east out of Iowa may
help churn some additional shower activity farther west out
toward I-39 where a handful of CAMs are resolving isolated
pockets, mainly during the latter part of the day. Latest
satellite trends show no distinct signs of new development
anywhere around the area so it may end up being more of a late
afternoon show, which adds confidence to there being little to
no impacts north of I-80. Whatever precip coverage does
materialize should wrap up by mid-evening as the trough axis
moves across stripping forcing and moisture from the area.

Broad, relative high pressure behind the departing system will
bring dry and mostly sunny conditions to Monday and Tuesday.
Highs are forecast in the lower 80s for Monday and mid 80s on
Tuesday. Onshore winds both days, however, will bring noticeably
cooler conditions to locales near the lake with afternoon temps
forecast in the lower and middle 70s around the lakeshore. The
vort lobe from today will get hung up across central IL and
central IN tomorrow and a handful of camps resolve pockets of
daytime showers and thunderstorms similar to today but confined
to our far southeastern CWA, if not outside of the CWA entirely.
Couldn`t argue with the NBM wanting to introduce some slight
chances for storm or two down there tomorrow. Mid-summer heat
will remain through the middle of the week with another synoptic
system favored to traverse the region during the mid-late week
period bringing additional opportunities for rain and
thunderstorms.

Doom

&&

.AVIATION /18Z TAFS THROUGH 00Z TUESDAY/...
Issued at 1223 PM CDT Sun Jul 5 2026

Aviation forecast concerns for the 18Z TAFs:

- IFR ceilings and MVFR visibilities linger across Chicago
  terminals this afternoon, with gradual improvement through
  late afternoon.

- Scattered SHRA expected this afternoon, lowest coverage around
  KRFD. Isolated TS possible, though greatest chances are
  expected southwest-south-southeast of the terminals.

- Winds generally NNE to NE through the period, with a period of
  10-15 kt winds late today/early this evening and again during
  the day Monday.

A slow-moving upper-level trough remains over the western Great
Lakes region early this afternoon, atop a lingering very moist
low-level airmass in the wake of a weak cold front which moved
through the area late Saturday. An area of IFR ceilings and MVFR
vis in fog lingers across the Chicago metro terminals at midday
with modest north-northeast low-level winds off of Lake
Michigan. This is expected to persist early this afternoon,
though slowly improve to low-MVFR cigs and VFR vis late. Modest
diurnal warming is also expected to result in development of
convective SHRA across the area (already occurring across LM),
which may produce brief IFR conditions in rain this afternoon.
Higher coverage (and greater TSRA chances) are expected to be
just off to the southeast-south and southwest of the terminals
this afternoon, and have maintained VCSH/PROB30 mention in TAFs
for SHRA. This activity should eventually shift south/southeast
of the terminals by this evening, with decreasing low clouds and
fog giving way to VFR condition tonight and Monday.

Surface winds have been generally north to north-northeast
through midday, but should trend more northeast with time and
persist into Monday. A period of 10-15 kt winds is likely late
this afternoon and early this evening. and again during the day
Monday.

Ratzer

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...None.

&&

$$

Visit us at weather.gov/chicago